Most of vehicles are provided with various safety devices and convenience devices in addition to essential components for running a vehicle. In operation of recent vehicles, such safety and convenience devices are now considered indispensable rather than simply incidental.
As a typical safety device currently applied to a vehicle, there is known an electronic stability control (ESC) unit. The ESC basically has an anti-lock braking system (ABS) functionality and a traction control system (TCS) functionality. The ESC includes various sensors that obtain information necessary in the operation of the ESC, a power generating unit that generates physical power to control components such as a brake, and a control unit that gathers the information obtained from the sensors, determines whether or not the power generating unit is operated, and controls the power generating unit. It is noted that, although the power generating unit may be a hydraulic unit or a pneumatic unit, most of the units generate power by driving motors, so that it is recognized that the power generating unit is implemented using a motor. In addition, the control unit is a circuit for controlling driving of a motor serving as the power generating unit and may be included in an electric control unit ECU currently employed in most of vehicles.
Some of convenience devices also use a motor as a power generating unit and drives the motor under control of a motor drive circuit.
FIG. 1 illustrates an exemplary motor drive circuit of the related art, and more particularly, an ECU drive circuit of an ABS unit.
Referring to FIG. 1, the motor drive circuit of the related art includes a battery BT, a control unit ECU, and a motor M. Since the control unit is generally implemented in the ECU as described above, it is denoted by “ECU” in FIG. 1.
In FIG. 1, a power voltage supplied from a positive (+) terminal of the battery BT is divided into a motor power voltage MPWR and a digital power voltage DPWR using different lines, and the divided voltages MPWR and DPWR are applied to the motor M and the control unit ECU, respectively. Similarly, a ground voltage supplied from a negative (−) terminal of the battery BT is divided into a motor ground voltage MGND and a digital ground voltage DGND using different lines, and is the divided voltages MGND and DGND are applied to the motor M and the control unit ECU, respectively. The motor power voltage MPWR and the motor ground voltage MGND applied to the motor M are utilized as power for driving the motor, and the digital power voltage DPWR and the digital ground voltage DGND are utilized as power for operating the control unit ECU.
The motor M receives the motor power voltage MPWR and the motor ground voltage MGND applied from the battery BT and is driven under control of the control unit ECU.
The control unit ECU includes a micro control unit (MCU), a motor driving IC MDIC, and a motor switch MSW. The MCU transmits a plurality of control signals EN, PWM, FSR_DRV for driving the motor M using the motor driving IC MDIC, and the motor driving IC MDIC outputs a switch control signal SWC for turning on or off the motor switch MSW in response to the plurality of control signals EN, PWM, and FSR_DRV. The signal EN out of a plurality of control signals is a control signal for activating the motor driving IC MDIC, and the signal PWM is a pulse modulation signal for adjusting a switching timing of the motor switch MSW. The signal FSR DRV is a signal for driving a solenoid valve (not illustrated in FIG. 1). The motor switch MSW is turned on or off in response to the switch control signal SWC applied from the motor driving IC MDIC to supply the motor power voltage MPWR to the motor M and drive the motor M.
Under a normal condition, if the switch control signal SWC output from the motor driving IC MDIC has a first level (for example, a high level), the motor switch MSW is turned on, so that the motor M is driven by receiving the motor power voltage MPWR. Otherwise, if the switch control signal SWC has a second level (for example, a low level), the motor switch MSW is turned off, so that the driving of the motor M stops.
However, the operation described above is performed under a normal condition. Since the motor power voltage MPWR, the digital power voltage DPWR, the motor ground voltage MGND, and the digital ground voltage DGND are connected to the battery through different lines using wires and connectors, the motor power voltage MPWR, the digital power voltage DPWR, the motor ground voltage MGND, and the digital ground voltage DGND applied from the battery BT may have a problem such as disconnection or poor contact of the corresponding line due to a user's mistakes, aging, and the like.
The motor power voltage MPWR, the digital power voltage DPWR, and the motor ground voltage MGND suffer from only a problem that the motor M is not driven. Meanwhile, if there is a problem such as disconnection or poor contact in the digital ground voltage DGND line that supplies the ground power supply to the ECU, a floating voltage may be generated on a signal output from each component of the control unit ECU including the motor driving IC MDIC. If the floating voltage flows into the switch control signal SWC that is a signal output from the motor driving IC MDIC, the motor switch MSW is turned on unintentionally, so that the motor M is driven continuously. Accordingly, the unintentional operation of the motor may hinder safe driving and shorten a service life of the motor. Furthermore, there is a problem that the motor switch MSW may be damaged by heat.
In Korean Patent Laid-open Publication No. 2013-0080505, there is discussed a technique of stopping a motor operation by detecting a short circuit. However, this technique is limited to an electric vehicle and is not suitable for a drive circuit of a motor included in the safety devices and the convenience devices of vehicles including a general purpose vehicle. In addition, since this technique is used to stop driving of a motor of an electric vehicle in the event of a short circuit and the like, it is not a countermeasure to the case where the power line is disconnected. In addition, since this technique is used to simply stop driving of a motor, it may fail to provide a capability as a motor.